Shabbir is correct. PR passes from a page to ALL followed outbound links regardless of whether they are links to internal pages on the same site or links to external pages on other sites.. content has nothing to do with it

This is interesting. So just to clarify, would you still call this an internal linking issue?

For ecommerce I would imagine most sites to have mostly back links to their top level domain and not to individual products or pages. So the internal page PR would be mostly dependent on internal linking and domain equity. Am I right? Or am I missing something? (I'm a bit new to this stuff.)

I run my own ecommerce site and am interested in in SEO, but don't think it is practical to build tons of deep links. So I rely on internal linking (not very well optimized now, but I'm learning). Is this a realistic understanding of my own SEO?
- Ben

If your internal page has less backlink compare to your home page then internal page will have less PR compare to home page.Mostly websites have more page-rank of home page because keyword of website will target home page of that site.